Passive capillary and gravity drainage system and method

ABSTRACT

A system for draining liquid from soil is disclosed. The system includes a passive capillary drain in combination with a core for gravity flow, including a sand top dressing layer, a native soil interface, and a rootzone, a curtain traversing from the sand topdressing layer through the native soil interface to at least one tube element, the at least one tube element pulling the water out of the soil with capillary suction, and a core central to the at least one tube element that moves excess water via gravity flow with capillary suction. The elements may be installed parallel at a 3 feet center and a depth of 10 inches, and/or may be installed vertically.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No. 13/399,708 filed on Feb. 17, 2012, which claims the benefit of U.S. Provisional Application No. 61/444,310, filed Feb. 18, 2011, which is incorporated by reference as if fully set forth.

FIELD OF INVENTION

The instant disclosure relates to drainage systems and methods, and, more particularly, to a passive capillary and gravity drainage system and method.

BACKGROUND

Turf grass areas, such as those on golf courses, are typically subject to moderate to heavy foot traffic on a daily or weekly basis. Excessive water retention in such areas is highly undesirable due to the damage that may occur as a result of foot traffic and other factors. Thus, turf grass areas are reconstructed to include some drainage capability. The soil profile of such areas is commonly constructed as an excavation into the soil native to the site. A high sand content root zone and frequently coarse sand or fine gravel sub-layers are subsequently placed within this excavation. Subsurface drainage from this essentially closed basin is necessary and is typically provided by drainage pipe spaced from three (3) to six (6) meters apart and placed in shallow trenches in the sub-grade soil. One example of such a turf soil profile is that used in putting greens by the United States Golf Association (“USGA”).

Depending on the availability of suitable root zone and gravel materials, a putting green soil profile typically consists of a 300 mm thick, high sand content root zone mix positioned above a minimally 100 mm thick, predominately fine gravel zone. The gravel rests on the sub-grade soil except when adjacent to drain line trenches, where the same gravel also fills the trench. The particle size distribution of the gravel typically conforms to engineering specifications for a drainage filter. Such conformity helps to ensure maintenance of layer integrity and suitable hydraulic performance of the gravel.

During and shortly after rainfall, the gravel layer of, for example, a USGA putting green, promotes rapid drainage of the root zone. Excess water exiting the root zone follows a nearly vertical path, employing the maximum extent of the gravitational gradient. The maximal distance drainage water must travel to exit the root zone is virtually the root zone depth, or approximately 300 mm. Lateral flow to the spaced apart drainage elements occurs mostly within the very high permeability gravel layer. The gravel drainage blanket beneath the finer textured root zone also creates a large difference in the pore size distribution across this interface. This large separation of predominate pore sizes within these adjacent media yields a capillary break in the vertical direction. Consequently, the lower portions of the root zone remain saturated (or nearly so) after drainage has virtually ceased. Depending on the particle sizes of the root zone and gravel materials used for a given installation, the thickness of this perched water zone may vary. For coarser root zone and finer gravel textures, a thinner perched water zone will form and the upper surface of the capillary fringe will still reside at sufficient depth to ensure adequate air-filled porosity near the soil surface. For finer root zone and coarser gravel textures, the perched water zone will be quite thick and may severely reduce the proportion of air-filled pores near the soil surface.

Surface slopes, such as those found on putting greens and athletic fields, also occur on or at the interfaces between soil layers within the profile. This is because profile layers are typically built to a uniform thickness across the green or field. When the interface between layers is well defined, and there is a wide disparity between soil textures of adjacent layers, the accumulation of water is subject to interflow. This down-slope movement of subsurface water is particularly evident in profiles with high permeability root zone media and greater root zone depths. Presumably, only a high permeability root zone would allow sufficient rates of interflow for the modest slopes of these systems. A deeper profile depth may provide a greater reservoir of soil water available for such flow. Consequently, the excess and perched water of a USGA green would in time migrate down slope resulting in lower soil water contents at higher elevation locations and higher water contents at lower elevation locations across the field or green.

This phenomena results in the need for localized hand watering of high elevation locations within some putting greens, a costly and time consuming operation. Thus, it is evident that a high sand content root zone placed over a gravel layer provides rapid drainage during and shortly after a rainstorm. However, after this rapid drainage phase has ended, excess and perched water that is retained in the root zone results in localized soil wetness and laterally non-uniform soil water content across naturally contoured putting greens and athletic fields.

The prior art includes technologies designed to address the excess and perched water problem. Commercial applications typically consist of using air pumps or blowers to apply a sub-atmospheric pressure within the gravel layer. The vacuum thus helps remove the excess and perched water. This, however, is an active process requiring motor driven blowers and functions only during such times that the vacuum is applied. Thus, there is a need for a system that effectively removes excess and perched water using existing drains, but that is passive, that is, requires no human or mechanical intervention, and that continues to function as long as excess water is present in the soil profile.

Therefore, there is a need for a passive capillary system in combination with a gravity system that effectively removes excess and perched water, in sufficient volumes, while using no energy, requires no human or mechanical intervention and that continues to function as long as excess water is present in the soil.

SUMMARY

A system for draining liquid from a layered soil profile is disclosed. The system includes a passive capillary and gravity drain including a sand topdressing layer, a native soil interface, and a rootzone, a curtain traversing from the sand top dressing layer through the native soil interface to the at least one tube element that passively collects the fluid proximate to the at least one tube element, the at least one tube element draining the fluid from the layered soil profile, and a core central to the at least one tube element that collects and moves the excess water with gravity flow.

BRIEF DESCRIPTION OF THE DRAWINGS

Understanding of the present invention will be facilitated by consideration of the following detailed description of the preferred embodiments of the present invention taken in conjunction with the accompanying drawings, in which like numerals refer to like parts:

FIG. 1 illustrates the passive capillary and gravity drainage system of the present invention;

FIG. 2 illustrates the core and the at least one tube element of the present invention;

FIG. 3, illustrates a layout of the present system according to an aspect of the present invention;

FIG. 4 illustrates a comparison of the present system to a conventional drainage system; and

FIG. 5 illustrates a method of drainage according to an aspect of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

It is to be understood that the figures and descriptions of the present invention have been simplified to illustrate elements that are relevant for a clear understanding of the present invention, while eliminating, for the purpose of clarity, many other elements found in soil and drainage systems. Those of ordinary skill in the art may recognize that other elements and/or steps are desirable and/or required in implementing the present invention. However, because such elements and steps are well known in the art, and because they do not facilitate a better understanding of the present invention, a discussion of such elements and steps is not provided herein. The disclosure herein is directed to all such variations and modifications to such elements and methods known to those skilled in the art.

The present system and method enables the drainage of surface water faster by placing the elements closer than conventional sand channel systems, such as at half the distance, for example. The elements of the present system provide fast free-gravity flow through a core, plus capillary suction through the surrounding parts of the element. For example, the elements of the present system may be placed 3 feet apart and 8 to 16 inches below the surface, and used a sand curtain to draw trapped surface water to the elements for fast, effective drainage.

Layering is common in putting green soils, and occurs when a sandy root zone overlays a finer textured native soil, which is typical after years of top dressing. In these push-up greens the interface is often too close to the surface, resulting in wet soil problems for the turf. For example in USGA greens, excess water tends to perch where the sandy root zone interfaces with the gravel layer. This perched water is held at a slight suction, so it is unable to enter conventional draining systems. The present solution is a drainage system that works two ways. The first way is that the elements are placed at the bottom of the narrow sand curtain, which gives water trapped at the soil interface an exit. The unique element has an open stainless steel mesh core to remove large amounts of water quickly through gravitational flow. The second way is the element is made of highly conductive fiber glass, in which the spaces between the fibers match the pore sizes of the sandy root zone. The result of the present invention utilizing these aspects is a system that drains fast with passive capillary and gravity drainage and wicks away excess soil moisture with capillary suction 24 hours a day without the use of active means such as motors, pumps or other energy input. A hanging water column may be created at the outlet by incorporating a gravity drop. This hanging water column may provide for further capillary suction. Any size drop may provide a hanging water column, but a drop in the range of 1 inch to 10 inches may provide the appropriate capillary suction. More specifically, a drop of approximately 4-8 inches, or even more specifically approximately 6 inch drop may provide the appropriate hanging water column. The present system creates an effective suction effect that follows the natural contours of the surface, is installed only where drainage problems exist, and helps improve turf health by providing better drainage to chronically wet soils.

Referring now to FIG. 1, there is shown a depiction of the passive capillary and gravity drainage system 100 of the present invention. The passive capillary and gravity drainage system 100 may include a sand topdressing layer 110, a native soil interface 120, a drain 130, at least one tube element 140, and a core 150.

Sand topdressing layer 110 may be located adjacent to, and usually above, native soil interface 120. This boundary with native soil interface 120 may cause water to be captured and prevented from draining. Rootzone may be included within the native soil interface 120. Drain 130 may include a curtain that traverses from sand top dressing layer 110 through the native soil interface 120 to at least one tube element 140 and core 150. At least one tube element 140 may utilize capillary suction to collect fluid proximate to at least one tube element 140 and thereby drain this fluid from the layered soil profile. Core 150 moves collected fluid, such as by using gravity, from at least one tube element 140 and drains 130 to remove fluid from the layered soil profile.

Sand topdressing layer 110 may arise from practice of topdressing soil, including golf greens, as described herein. This practice has also been extended to fairways, sports fields and other prepared soil landscaping areas. Sand topdressing layer 110 may cause layering which occurs when a discrete layer of sand or thatch is formed over the rootzone, as discussed. This discrete layer may act as an impediment to the movement of water and oxygen. Sand topdressing layer 110 may include sand that is compatible with the existing rootzone material. Topdress/rootzone compatibility may be determined by performing a particle size analysis on the existing rootzone material and the proposed topdress.

Topdressing is the process of adding a fine layer of quality soil to the surface. Topdressing benefits the lawn as it builds up the quality of the soil over a period of time. By adding topdressing, sandy soils may be able to retain moisture to allow the lawn to be more resistant to drought, and clay soils may drain better to thereby improve root development. Another benefit of top dressing may be to help even out any lumps and bumps that are present on an uneven lawn, green, or field by filling in any small hollows that may have developed. Top dressing may also stimulate the grass to produce new shoots and thereby may result in denser grass cover which helps combat the onset of weed and moss infestation.

Native soil interface 120 may include the interface that has been dressed with the top dressing. Native soil interface 120 may be created without the presence of a sand topdressing layer 110. Native soil interface 120 may occur at any barrier to the transfer of materials including water, for example. Native soil interface 120 may create a barrier for the transfer of materials, such as nutrients and water, between layers. Water, nutrients and roots have distaste for passing between dissimilar levels. The present invention provides a system that penetrates, or pierces, this native soil interface 120 in order to allow moisture and water to drain therefrom.

Drain 130 may be formed using a narrow sand curtain, for example. Drain 130 may be a portion of a drainage system 100 that includes a multitude of drains separated apart by 3 feet. Such a drain 130 may include a ⅜ inch sand curtain spaced apart at 3 feet spacing, for example. Drain 130 may be installed within a layered, turf soil profile. Drain 130 may be oriented vertically and span from the sub-grade soil surface to about 100 mm into the lower portions of the root zone exiting into existing gravel or parallel passive capillary lines. That is, drain 130 may provide a path from the perched fluid to at least one tube element 140 and core 150. Drain 130 may take the form of a sand curtain with a dimension of approximately ⅜ inches. Drain 130 may provide a continuous pathway of capillary pores from the lower reaches of the root zone and through the gravel layer, thus eliminating the capillary break present in layered soils created by the top dress/native soil interface 120. Drain 130 may have a small diameter (c.a. <1 inch) so that installation will minimally disrupt the existing root and environment. In an exemplary embodiment, drains 130 are spaced apart (c.a. 3 feet) as to not inhibit the lateral flow characteristics of the gravel layer. Furthermore, drain 130 may maintain physical integrity within the gravel layer when lateral flow conditions exist. Finally, drain 130 may have a sufficient flow capacity to allow timely removal of the excess and perched water. This flow capacity may be based on particle size and a comparison of the particle size to the surrounding sections, such as the top dress and rootzone, for example.

To effectively and efficiently remove perched water in a layered profile, a passive capillary drain of the present invention typically includes a distribution of pore sizes and compatibility with the root zone to provide a continuous pore pathway spanning the gravel layer. If the majority of pores in capillary drain 130 are substantially larger than the rootzone, a capillary break may occur at the interface between the capillary drain 130 and roots, thereby disrupting the pathway. However, if the pores of drain 130 are substantially smaller than the root zone, drain 130 would have insufficient hydraulic conductivity to convey flow in a predictable and efficient fashion.

At least one tube element 140 may be designed to draw and capture water through capillary or other physical actions when excess water is present and/or water is perched adjacent to, above, or below element 140. Another aspect of at least one tube element 140 is that fines do not clog the pores due to the relatively slow water velocity under the surface.

In an exemplary embodiment, fiberglass rope may be utilized for constructing at least one tube element 140 of the present invention. The water retention and hydraulic conductivity properties of some commercially available fiberglass ropes, as well as the use of fiberglass as a passive capillary sampler of soil, is known in the art. Ropes ranging in diameter from about 0.25 to 1 inch (0.64 to 2.54 cm) have been shown in the scientific literature to have water retention and conductance characteristics compatible with the method of the present invention. According to an aspect of the present invention, at least one tube element 140 may take the form of a fiberglass weave of elements, such as a 1 inch diameter fiberglass weave, that draws water through a capillary action when water is perched around, near, below, or above at least one tube element 140.

Flow capacity values are the product of the hydraulic conductivity and cross-sectional area of passive capillary drains. These values give the volume of water per unit time that is conducted through a capillary drain under a unit hydraulic gradient as would occur in a vertically oriented installation. Flow capacity for single strands range from 152 nearly 2000 cm³/hour, and doubling the number of strands may increase the flow capacity two-fold. Thus, a wide range of flow capacity values exist resulting from the diversity of materials that may be used, including a large array of fiberglass rope materials that are commercially available.

As previously described, the exemplary embodiment of the present invention utilizes fiberglass rope for accomplishing capillary drainage. There are, however, a variety of materials that may serve as tube element 140 including fiberglass tape, a weaving or webbing of fiberglass or metallic strands having a rectangular cross-section and contained column of sand or other mineral particles does contain, which may consist of a tubular knitted mesh filled with appropriately sized sand particles. These alternative materials are wettable, contain a distribution of pore sizes that are compatible with the root zone, have an adequate flow capacity to allow timely removal of excess and perched water, and have a structural integrity that would resist free water flow.

Referring now also to FIG. 2, there is shown a blowup of core 150 and at least one tube element 140 of the present invention. Core 150 of the present invention is designed to increase the flow rate of water once contained in the passive capillary and gravity drain. Core 150 may be made from a number of materials or combinations thereof, such as stainless steel tubing, flexible plastic tubing, ceramics, or other material capable of moving water and allowing water to enter a drain. Core 150 may also take the form of a plastic, or other suitable material that provides drainage, tube with slits positioned to allow captured fluids to enter the tub and be drained according to the present invention. Several common materials may be found in the landscaping industry, for example. According to aspect of the present invention, core 150 may take the form of a ⅜ inch stainless steel stint or tube, for example. According to another aspect of the present invention, core 150 may take the form of a stainless steel mesh core that carries drainage water away with high efficiency, for example, during the first several hours following a heavy rain.

Referring now to FIG. 3, there is shown a layout of the present system 300 according to an aspect of the present invention. As may be seen in FIG. 3, there are a multitude of capillary drains 310 forming a system according to an aspect of the present invention. System 300 may include drains 310 formed on 3 feet spacings and attached to a larger drain 320, or collection system that is in turn connected to an outlet 330 for the drain water.

Referring now to FIG. 4, there is shown a comparison of the present system to a conventional drainage system. A conventional drainage system refers to a 2-inch perforated polymer pipe configured with a 6 foot spacing. The present system, as compared to ditch excavating with additional 2 inch plastic pipe systems, allows for faster installation, is extremely cost effective, and may provide a site-specific solution to treat only the low areas. Further, the present invention may be installed at 3 feet spacing for more consistent draining, dual acting gravity and capillary action, to enhance existing drainage systems.

As may be seen in FIG. 4, the present capillary drainage system 100 may handle more than 2× the amount of drainage water in the initial four hours of drainage. Further, the capillary drainage system 100 of the present invention may continue to work as well as a conventional drainage system for the time 8-24 hours after the drainage begins. The present invention provides superior drainage during the first four hours and through the first eight hours while maintaining equal or better drainage for the remainder of the initial 24 hour drainage period.

FIG. 5 depicts the steps in a method 500 of moving water. Method 500 includes capturing 510 a first plurality of the water in a core and drawing 520 a second plurality of water into a tube element. Method 500 may include removing 530 fluid that is perched at the native soil interface using a sand curtain. Method 500 may also include providing 540 a hanging water column to increase the capillary forces used in fluid removal. Further, method 500 may include draining 550 the captured fluid into an existing drain or collection line.

The system and method of the present invention may be used anywhere it becomes necessary to move water. For example, sports fields, golf courses, foundations, bridges, construction areas, rooftop gardens, planters, and other drainage areas may benefit from the present invention. In the case of golf courses, the highly effective drainage on chronically wet soils provides a benefit, in addition to the benefit of the low cost and lack of use disruption. The present system is extremely cost effective and may pay dividends for schools, universities, and municipalities to improve drainage and natural grass playing fields making maintenance easier and less expensive.

The present system may be installed with a minimally disruptive vibratory plow, allowing the elements of the present system to be surgically placed at 3 feet intervals, leading to better drainage.

In the case of horizontal installation, installation may begin with a layout and cutting of an entry hole using a cup cutter or similar tool. Using a vibratory plow with a special blade and sand chute, a ½ inch sand curtain from 2 inches below the surface to the top of the elements is installed. The elements of the present invention may be installed 8 to 16 inches below the surface. These lines run parallel at 3 foot spacing and move water using capillary and gravity flow to a collection line or existing drain. Once collected at a collection line or existing drain, a drop may be incorporated to provide a hanging water column. This hanging water column may provide for increased capillary suction. Any size drop may provide the hanging water column, but a drop in the range of 1 inch to 10 inches may provide the appropriate capillary suction. More specifically, a drop of approximately 4-8 inches, or even more specifically approximately 6 inch drop may provide the appropriate hanging water column.

In the case of a vertical installation, the capillary and gravity drain installation may include a two-step procedure. First, a pilot hole is created in the soil extending from the surface to the maximum depth of drain insertion. Subsequently, the capillary drain material is inserted into the pilot hole. As the pilot hole needs to extend through both the sandy root zone and a layer of fine gravel, it is desirable to employ a solid, pointed tip, circular diameter tine to create the pilot hole of a diameter slightly larger than the capillary drain. A mechanical actuator, such as a hydraulic ram, for example, may be used to drive the tine vertically into the soil and remove it leaving a pilot hole. To facilitate insertion of a flexible capillary drain (such as a fiberglass rope) to the desired depth, some added stiffening support may be required. Enough stiffness may be obtained by choosing the right material for the core 150. Inserting and affixing a small diameter wire, plastic or wooden dowel into the center and along the long axis of the rope may provide additional stiffening support. The modified section of fiberglass rope may then be inserted to the desired depth. The resultant cavity extending from the soil surface to upper surface of the capillary and gravity drain is then closed with tape, foam or other suitable material. The still open space is backfilled with appropriate root zone material.

The installation methods described above may also include mechanization of the insertion process so that a single operator of a small, motorized unit could, in a timely fashion, install an array of drains within a green.

Additionally, the present invention may provide for the ability to back pressure the drains using a pump thereby enabling aeration of a soil or rootzone. Such aeration may be accomplished by connecting a pump to the output, somewhere in the system accessible while minimizing green/rootzone disruption, and pressurizing the system to add and/or stimulate aeration of the rootzone.

Although the invention has been described and pictured in an exemplary form with a certain degree of particularity, it is understood that the present disclosure of the exemplary form has been made by way of example, and that numerous changes in the details of construction and combination and arrangement of parts and steps may be made without departing from the spirit and scope of the invention as set forth in the claims hereinafter. 

What is claimed is:
 1. A method of installing a system for draining liquid from a soil surface, the method comprising: installing a plurality of tube elements each including a central core approximately one foot below the surface, wherein adjacent ones of the plurality of tube elements are substantially parallel to other ones of the plurality of tube element, the installed plurality of tube elements draining liquid using capillary suction and gravity flow; creating a sand curtain extending from just under the surface to the top of the plurality of tube elements to eliminate a capillary break of the soil by providing a continuous pathway of capillary pores to drain liquid from the soil surface to the plurality of tube elements; and installing a drain with a drop to incorporate a hanging water column to provide for increased capillary suction of the plurality of tube element to enhance the draining of the liquid from the soil.
 2. The method of claim 1, wherein creating of the sand curtain comprises a vibratory plow.
 3. The method of claim 1, wherein just under the surface is approximately two inches below the surface.
 4. The method of claim 1, wherein the sand curtain created is approximately one-half inch long.
 5. The method of claim 1, wherein the plurality of tube elements are installed from 8 to 16 inches below the surface.
 6. The method of claim 1, wherein the plurality of tube elements is spaced using an approximate three-foot spacing between adjacent tube elements.
 7. The method of claim 1, wherein the drop is in a range of approximately 1 to 10 inches.
 8. The method of claim 1, wherein the drop is in a range of approximately 4 to 8 inches.
 9. The method of claim 1, wherein the drop is approximately 6 inches.
 10. The method of claim 1, wherein the sand curtain is less than approximately one inch in diameter.
 11. The method of claim 1, wherein the sand curtain is less than approximately ⅜ inches in diameter.
 12. The method of claim 1, wherein the core comprises a stainless steel mesh.
 13. The method of claim 1, wherein the plurality of tube elements comprise fiberglass elements.
 14. The method of claim 1, wherein the sand curtain comprises another of the plurality of tube elements include a rigid core. 